1. Field of the Invention
The present invention relates to mountings for filter cartridges and, more particularly, to seals for sealing opposed ends of a filter element of a filter cartridge that accommodate for axial movement of the filter cartridge without compromising the seals.
2. Description of Related Art
Filter cartridges have been in use for decades to filter with a cylindrical filter element a fluid flowing radially therethrough. Usually the fluid flow through the filter element is from its external surface to its internal surface. Thereafter, the fluid is exhausted axially from one end. Each opposed end of the filter element include a compressible annular cap mating with an annular knife edge of a housing. Each annular knife edge forms a seal with the respective end cap as a function of the compression therebetween imposed by the housing and the elasticity and resiliency of the filter element. Over a period of time, the end caps tend to acquire a set and the pressure against the corresponding annular knife edge diminishes to the point where the seal is compromised.
The resiliency and elasticity of the filter element providing a bias against the opposed annular knife edges diminish over a period of time or through deterioration caused at least in part by interaction with the fluid being filtered. The loss of resiliency and elasticity compromises the bias force against the opposed annular knife edges. The pressure differential on opposed sides of each annular knife edge increases as the filter element becomes more and more clogged. Such increase in pressure differential, coupled with the compromised sealing bias, will cause leakage. The resulting leakage will contaminate the previously filtered fluid with potentially disastrous results.
The previously known solution to extend the filtering life of a filter cartridge has been that of increasing the pressure bias of the annular knife edges on the opposed ends of the filter element. At best, this solution increases the life of the sealing function of the annular knife edges for a limited period of time.
Another problem with conventional filter cartridges is that tolerances of filter cartridges from different manufacturers are not the same. Thus a presumably standard sized filter cartridge may not fit a housing for such filter cartridge sufficiently well to maintain a seal for a reasonable period of time before being affected by the above described modes of deterioration.